The present disclosure relates to a solid-state imaging device, a manufacturing method thereof, and an electronic apparatus.
Electronic apparatuses such as a digital video camera or a digital still camera include a solid-state imaging device. For example, the solid-state imaging device includes a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor.
In the solid-state imaging device, a plurality of pixels are arranged on a pixel region of a substrate. A photoelectric conversion portion is provided on each pixel. For example, the photoelectric conversion portion is a photodiode, and receives incident light through the light sensing surface and generates a signal charge by performing a photoelectric conversion with respect to the received light.
Among the solid-state imaging devices, in the CCD type image sensor, a vertical transfer portion is provided between a plurality of pixel columns which are vertically lined up in a pixel region. In the vertical transfer portion, a plurality of transfer electrodes are provided so as to be facing a vertical channel region through gate insulating films, and the vertical transfer portion is configured so as to transfer the signal charge, which is read from the photoelectric conversion portion by a charge readout portion, in a vertical direction.
In contrast, in the CMOS type image sensor, pixels are configured so as to include a pixel transistor in addition to the photoelectric conversion portion. The pixel transistor is configured so as to read the signal charge generated by the photoelectric conversion portion and output the read signal charge to a signal line as an electric signal.
In general, in the solid-state imaging device, the photoelectric conversion portion receives light incident from a front surface side on which circuit elements, wirings, or the like are provided in a substrate. In the cases of the “front surface illumination type”, since the circuit elements or wirings shield the incident light, it may be difficult to improve sensitivity.
Thereby, “a rear surface illumination type” has been suggested in which the photoelectric conversion portion receives the light incident from a rear surface side which is a side opposite to the front surface on which the circuit elements, the wirings, or the like are provided in the substrate. Also in the “rear surface illumination type”, the incident light entering one pixel may not enter the photodiode of this one pixel and enter photodiodes of adjacent other pixels. For example, when the incident light enters in a largely inclined state, the light does not enter the photodiode of the pixel just below the light and enters the photodiodes of other pixels. Thereby, since noise is included in the signal due to the optical phenomenon, quality of the captured image may be decreased. In order to suppress occurrence of this disadvantage, light shielding films are provided between a plurality of pixels (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2010-109295 and 2010-186818).
Moreover, in the solid-state imaging device, in order to suppress a dark current from being generated due to an interface state of the semiconductor substrate on which the photoelectric conversion portion is provided, the photoelectric conversion portion of an HAD (Hole Accumulation Diode) structure has been suggested. In the HAD structure, since a positive charge (hole) accumulation region is formed on a light sensing surface of a n-type charge accumulation region, occurrence of the dark current is suppressed. In addition, in order to form the positive charge accumulation region in the interface portion of the photoelectric conversion portion, further suppressing occurrence of the dark current by providing “a film having a negative fixed charge” as a pinning layer has been suggested. For example, a high dielectric constant film such as a hafnium oxide film (HfO2 film) is used as the “film having a negative fixed charge” (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-306154 or the like).
Moreover, in the solid-state imaging device, in order to prevent the signal outputs from each pixel from being mixed due to electric noise, a pixel separation portion which electrically separates a plurality of pixels is provided. For example, the pixel separation portion is provided by ion-implanting impurities to the semiconductor substrate.